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Coral reef connections

Scientists have identified how coral reefs, hundreds of miles apart, are connected by ocean currents. Observing these networks from space may prove vital for their conservation.

Coral reefs are among the most biodiverse ecosystems on the planet. They occupy less than 0.2% of the world’s oceans, but support a treasure trove of life - around 35% of all known marine species are found on and around reefs. They are, however, under threat; climate change, ocean acidification and a range of human activities are all affecting these fragile ecosystems. Resilience to these threats is stronger when the reefs are better connected, sharing a flow of life and genes between them that helps to maintain healthier populations, but such connections are not easy to identify.

By bringing together satellite observations, genetic population data and model simulations, a team led by Plymouth Marine Laboratory (PML) scientists has now traced this connectivity. Dynamic circulation features in the Red Sea, such as eddies and currents, form pathways along which marine life can flow. And at the source of these pathways are invaluable ‘mother reefs’ spreading life to other Red Sea reefs. These ‘mother reefs’ are perhaps the most important reefs of all when considering management and conservation strategies, suggests lead author Dionysios Raitsos, of PML.

“Essentially, these reefs are ‘population donors’, enhancing gene flow around the Red Sea, and their conservation should be prioritised over other reefs,” said Raitsos.

Initial conclusions were based on the connectivity between reefs observed from satellites in space. To establish if these findings had any real ecological substance, the team tested the results against the genetics of the Red Sea’s anemonefish (Amphiprion bicinctus) population. The predictions of connectivity were remarkably consistent with population data, demonstrating how currents and circulation form pathways for larval stages of marine life around the Red Sea.

Connectivity models often require costly approaches and data that are difficult to collect. This research instead showcases a cost-effective tool and method, using freely available satellite data-sets to enable the estimation of connectivity remotely, and guide more effective management of waters where oceanographic information may be in short supply.

“Discovering how coral reefs are connected and how water circulation in the Red Sea carries life to distant reefs is vital in furthering our understanding of these vulnerable ecosystems,” said Raitsos. “Our findings and cost-effective approach can benefit conservation and management efforts on coral reefs around the world.”

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